Industrial applications of light olefin-containing hydrocarbons, and particularly liquified propylene, have become more increasingly specialized. The technology as presently developed utilizes highly efficient catalysts to convert these light olefins into final products such as polymers, any excess being recycled. The latest technology in propylene polymerization uses as solvent the propylene itself, the large excess of which is recycled. Since these highly efficient catalysts are very sensitive, impurities in recycled olefins may deactivate them at least partially, leading to a productivity decrease. Further, some impurities may gradually accumulate in the recycle stream. It has also been observed that some properties and particularly the melt flow index of the polymers is unstable as a function of time.
As a result, there is a real need to improve techniques for the polymerization of olefins, more particularly when high yield catalysts are used.